MIDI is the acronym for
Musical Instrument Digital Interface. This is the electronic standard to
allow musical instruments to communicate. SMF is the acronym for Standard
MIDI Files. An SMF file contains all the information necessary to play back
pre-recorded or composed (sequenced) music. SMF format type 0 is the one
compatible with most playback devices. You can find lots of details on
MIDI using any search engine. Some frequently asked questions are answered
at ALT.MUSIC.MIDI.
There are lots of other sites with similar midi help.

There are literally
thousands of MIDI files (songs) on the Internet to download , edit if you
desire, put on a floppy and play on the MIDI capable piano or keyboard. To
play on a Yamaha Disklavier or similar piano you should make sure the file is
SMF Type 0, although newer units will also play Type 1. Next, the file should have the
piano parts on channel 1 (or 1 and 2) and set as Acoustic Grand (see your piano instructions for specifics). If you plan to do a lot of
Internet downloading I would suggest finding shareware (see below) or purchasing music editing software such as
Yamaha's XGWorks, Cakewalk, or PowerTracks Pro Audio.. I use Cakewalk Home Studio
9. It's been around for years and is very popular. Although it is not real rich in documentation,
basic editing is fairly easy to learn using the help files. At the bottom
of this page is a link
to a retailer of the product. Cakewalk.com
also has a trial version that you can download and try, but the link below gives
about a 30% discount. It's also available (good info in reviews) at Amazon.com.For PowerTracks go to pgmusic.com.

It sounds difficult
to use Midi files on my Disklavier or other device. How do I get started?

I would first try downloading piano solo midi
files. Try the links shown below ( right click on the midi file you desire and
save link to your computer). Play them on your computer before
making a floppy, and then try them on the piano. I would be ready to
adjust the disklavier volume control as they load since some are set at a high volume when created
(For files I want to keep, I initially reset the files volume settings to 100 or
less (try 80), using Cakewalk). While this will help volumes in general,
there are more sophisticated ways of adjusting volumes and note velocities that
have been discussed on the user groups and can be tried later. If all else fails, read the Yamaha Disklavier or other device manuals.
One other very important item ... I would definitely join the Disklavier
Users Groups and also browse their archives (see links below). This
alone could save you hours of trial and error and frustration.

Software is
available to scan sheet music and convert it to a MIDI file. Musitek came
out with a product a few years ago called MIDISCAN that does just that.
They have improved on it since then and now have a couple of other products that
are better (Smartscore and Piano Edition). There will still probably be a
large amount of editing required but it can be useful.